1. Field of the Invention
The present invention relates to a dry multilayer analytical element containing an oxidized coenzyme and a process for the preparation of said element.
2. Description of Prior Art
Reactions in which dehydrogenase and a coenzyme are involved have been widely employed in clinical chemical analyses. For example, various reaction systems in which a dehydrogenase such as glycerol dehydrogenase, cholesterol dehydrogenase, lactate dehydrogenase, alcohol dehydrogenase, glutamate dehydrogenase, aldehyde dehydrogenase, .alpha.-glycerophosphate dehydrogenase or glucose-6-phosphate dehydrogenase participates are employed for quantitative determination of substrate such as triglyceride, glycerol, cholesterol, lactic acid, glutamate, glycerol-3-phosphoric acid or glucose-6-phosphoric acid, and an enzyme such as aspartic acid aminotransferase (AST), lactate dehydrogenase (LDH), amylase or creatine kinase (CK). Through the reaction, quantitative analysis can be made by directly measuring increase or decrease of the amount of a reduced coenzyme. However, the conventionally employed NADH (i.e., nicotinamide adenine dinucleotide) or NADPH (i.e., nicotinamide adenine dinucleotide phosphate) has its maximum absorption peak at approx. 340 nm, and therefore the photometric measurement requires an expensive photometer for the measurement of a light in the ultraviolet region. Another drawback resides in that such measurement of a light in the ultraviolet region is easily influenced by a variety of coexisting compounds.
An alternative photometric analytical method using an electron acceptable dye-forming compound and an electron transmitter (i.e., carrier) in combination for forming a dye having an absorption peak in the visible ray region upon contact with the produced NADH was proposed for replacement of the above-described method of directly measuring the produced NADH (or NADPH). This method, however, has a drawback that a positive error is introduced if a liquid sample contains dehydrogenases other than the dehydrogenase to be analyzed. Particularly, in the case of analyzing a human serum, the electron acceptable dye-forming compound sometimes reacts with a reduced nicotinamide coenzyme produced by reaction with lactate dehydrogenase (LDH) and lactic acid, to give a colored product. Japanese Patent Provisional Publication No. 55(1980)-104899 describes that the erroneous coloring of the electron acceptable dye-forming compound is obviated by incorporating pyruvic acid into the reaction system.